6 Sequences, Arrays, and Vectors

The sequence type is the union of two other Lisp types: lists
and arrays. In other words, any list is a sequence, and any array is
a sequence. The common property that all sequences have is that each
is an ordered collection of elements.

An array is a fixed-length object with a slot for each of its
elements. All the elements are accessible in constant time. The four
types of arrays are strings, vectors, char-tables and bool-vectors.

A list is a sequence of elements, but it is not a single primitive
object; it is made of cons cells, one cell per element. Finding the
nth element requires looking through n cons cells, so
elements farther from the beginning of the list take longer to access.
But it is possible to add elements to the list, or remove elements.